An aircraft can encounter icing conditions during when it flies through a cloud containing supercooled droplets having nonzero liquid water contents (e.g., up to 2.5 grams of water per cubic meter of air). As a general rule, for a thermal ice protection system, the most severe icing conditions will occur when the temperature is at its coldest (e.g., approaching −22° F.), the relevant speed is the fastest, and mean droplet size is relatively large (e.g., nearing 50 micrometers). An ice protection system must be designed to protect an aircraft from the most severe conditions.